New flavonol triglycosides from the leaves of soybean cultivars.

Soybean (Glycine max) is a major crop in the world. Three new flavonol 3-O-glycosides, kaempferol 3-O-alpha-L-rhamnopyranosyl-(1 --> 4)-[alpha-L-rhamnopyranosyl-(1 --> 6)-beta-D-galactopyranoside] (1), kaempferol 3-O-alpha-L-rhamnopyranosyl-(1 --> 4)-[beta-D-glucopyranosyl-(1 --> 6)-beta-D-galactopyranoside] (4) and quercetin 3-O-beta-D-glucopyranosyl-(1--> 2)-[alpha-L-rhamnopyranosyl-(1 --> 6)-beta-galactopyranoside] (5) were isolated from the leaves of soybean cultivars, together with three known compounds, kaempferol 3-O-beta-D-glucopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1--> 6)-beta-D-galactopyranoside] (2), kaempferol 3-O-beta-D-glucopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1 --> 6)-beta-D-glucopyranoside] (3) and quercetin 3-O-beta-D-glucopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1 --> 6)-beta-D-glucopyranoside] (6), and also common flavonoids. The isolated compounds possess similar structures and high water solubility, and so it was hard to isolate them (in particular 5 and 6) with a normal preparative HPLC system. Their final purification was achieved by a preparative HPLC system equipped with a recycle device.